Antisubmarine attack method



United States Patent Inventors Robert H. Mathes Hillcrest Heights, Maryland; Lauro C. Ricalzone, Forest Heights, Maryland App]. No. 188,006

Filed April 12, 1962 Patented Sept. 1, 1970 Assignee The United States of America as represented by the Secretary of the Navy ANTISUBMARINE ATTACK METHOD 5 Claims, 7 Drawing Figs.

U.S. Cl 114/20, 340/3,178/7.83 Int. Cl "1 42b 19/00, GOls 9/66,l-101i 29/34 Field of Search 1 14/20,

[56] References Cited UNlTED STATES PATENTS 2,586,743 2/1952 Thresher et al 178/783 2,689,083 9/1954 Hammond 235/615 2,696,610 12/1954 Turley 178/783 3,093,808 6/1963 Tatnall et a1. 340/2 3,092,803 6/1963 Wolffet al 340/3 Primary Examiner Benjamin A. Borchelt Assistant ExuniinerThomas H. Webb Artorney- R. I. Tompkins and R. S. Sciascia ABSTRACT: The invention is directed to a method of utilizing long range sonar equipment for locating and classifying a distant underwater object, dispatching a high speed vehicle carrying a small sonar transponder and weapon to the immediate vicinity of the underwater object, transmitting relative range and hearing intelligence as derived from received sonar from said transponder, by electromagnetic waves to the vehicle for accurate delivery ofa weapon to the object.

Patented .Sept. l, 1976 I of2 Sheet INVENTOR5 ROBERT H. MATH ES ATTORNEY Patented Sept. 1, 1970 3,526,198

INVENTORS RO RT H. MATH ES LA 0 C. RICALZONE ATTORNEY ANTISUBMARINE ATTACK METHOD The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

-The present invention is directed to a method for locating classifying, and destroying underwater objects. More specifically the invention relates to a method employing sonar for antisubmarine warfare.

In order to detect submerged submarines successfully it has been necessary to use long range pulse echo sonar. The capability of modern submarines has been so improved that surface ships can no longer rely on speed and maneuverability for protection. Sub-chasers must, therefore, be able to detect their prey and attack from greater distances. To achieve this, sonars have been developed which have long range capabilities. Since contacts made with this equipment tend to be less positive, the more informative and reliable pulse echo mode is preferred.

The pulse echo equipment used in sonar work has several drawbacks, however, which tend to limit its use in anti-submarine warfare. One of these is inaccuracy due to lack of resolution. Another is confusion due to the multiplicity of sound paths encountered. Still another is sluggishness due to the low speed of sound in water as compared to radar and optical locating systems. There is also a degree of uncertainty due to the fact that sound will be reflected from any hard surface or even bubble formations present in the propagating medium.

An object of the present invention, therefore, is to provide a method of employing long range sonar with both low speed and high speed vehicles for maximum effectiveness.

Another object of the invention is to provide a combination of long range sonar equipment and related equipment with various types of transporting vehicles to provide an effective anti-submarine attack unit.

These and other objects and attendant advantages of the present invention will be best understood with reference to the following specification taken with the accompanying drawings wherein:

FIGS. la through If show the elements of the attack unit and the method in which they operate during an attack; and

FIG. 2 shows a rotatable overlay used in combination with the cathode-ray-tube shown in FIG. 1.

Referring to FIG. la one example of a suitable combination of basic elements for an attack system are shown. In the foreground a submarine under attack is indicated and this will generally be submerged. In the background is an attacking vessel 11, which 'in some cases may have a top speed less than that of the submarine. A sonar beam is shown emanating from the longe range pulse echo sonar equipment aboard the vessel 11. In the upper left hand corner, the face of a cathode-raytube, 13 which is used to display the information obtained by the sonar equipment, is added to show the relative positions of the blips produced by the vessel V and the submarine S.

FIG. lb shows the same elements a short time later and also a high speed vehicle, in this case a helicopter 14, which has been dispatched to the range and bearing of the submarine as obtained by sonar. The helicopter may be launched from the vessel 11 or from a nearby land base. The most convenient method of navigation is employed to guide the helicopter and may involve any system from radar to dead'reckoning.

FIG. 1c shows the elements a bit later when the helicopter arrives at approximately the range and bearing indicated by the sonar equipment. When all of the information available indicates such a point has been reached a sonar transponder is ejected from the helicopter and its position in the water marked by a buoy, dye marker or other suitable means. For this purpose a device called a posit buoy has been developed.

The posit buoy consists of two parts, one heavier and the other lighter than an equal volume of water. Upon impact with the water the heavier part sinks below the water surface where it is supported by a line fastened between it and the lighter buoyant part. The lighter part is painted to contrast with the water and carries lights or radio transponders so that its position may be quickly ascertained and relayed to the helicopter. The heavier part contains a sonar transponder and appears on the sonar display, as indicated by point P on the cathode-raytube, in response to the first subsequent sound pulse from that equipment. Theoretically points P and S should coincide.

There are various reasons why the points P and S do not usually coincide. There will be more or less error in the course of the helicopter depending on the type of navigation used. Also, the sonar beam at long ranges is affected greatly by thermal gradients in the propagating medium. The beam is generally sufficiently refracted that it reflects from at least one interface at the surface or the bottom of the water medium. The subsequent delay and angular deviations affect both the range and bearing.

Fortunately, however, it can be assumed that echoes received from the submarine and the transponder are similarly distorted. The discontinuities found in the water medium do not change abruptly, but extend over broad areas. Since the transponder and submarine are closely spaced compared to distance from each to the vessel 11, it can be safely assumed that both signals travel down the same narrow sound channel through the same discontinuities.

FIG. 1d shows the relative position of the elements in the attack unit at a later time, as a result of the information received from the transponder. Since the transponder and submarine echo signals suffer substantially the same distortions in transit, the difference between the two can only be due to a real dis placement as indicated by the vector PS. The range and bearing of this vector is transmitted to the helicopter over a radio link, which permits the helicopter to fly directly to the sub.

FIGS. 12 and Ifshow the last steps of the operation. As the helicopter passes over the submarine it drops an appropriate weapon 16 (shown in la) in this case an acoustic homing torpedo. The weapon searches as shown in FIG. If until it finds and destroys the submarine.

Certain alternative procedures and apparatus may be used in carrying out the above described attack method. The use of display equipment makes it possible to determine visually the information supplied to the helicopter, the information being relayed by radio between the sonar operator and the helicopter pilot. However, since the range and bearing information for both the transponder and the target is available in similar electrical signal form, the two are easily compared in simple logic circuits as found in many electronic data computers. The output of such a computer can directly control an autopilot aboard the helicopter and also direct the release of the weapon at a predetermined time. If the weapon has a greater speed than the helicopter and sufficient range it may be dropped earlier near the transponder after being directed on a bearing to the target.

Additional apparatus that can be used in carrying out the method are lighter-than-air craft, hydrofoil ships and fixed sonar stations. Some work has been done to adapt blimps for sonar work. I-Iydrofoil craft show considerable promise as both a sonar vessel and a weapon carrier. Since the method does not require movement of the sonar equipment or exact knowledge of its location, an attack may be directed from a shore station connected to an array placed without precision on the ocean floor.

FIG. 2 shows an overlay which may be used with the long range sonar equipment to aid the operator in an attack. The overlay has a metal body portion 20 in the form ofa short hollow cylinder. One end of the body portion is closed by a transparent window 21 which rests in a groove therein. The dimensions of the window are sufficiently less than those of the groove to make the former freely rotatable. The end of the body portion is calibrated circumferentially in bearing angles. The window is calibrated radially with a series of equally spaced parallel range lines radially disposed. One such series is provided for each rate of range sweep provided by the sonar, the range lines being spaced according to the distances represented by each sweep.

To use the overlay, it is centered on the face of the cathoderay-tube in the sonar set with zero bearing to the North. The window is then rotated so that the appropriate set of range lines is normal to an imaginary line between the blips representing the submarine and the transponder. In this position the range lines radiate toward the bearing of the imaginary line and the range between the two blips is read by counting the number of range lines therebetween.

Such a device is easily constructed by one skilled in the machine shop arts. The body may be made of steel and the window from Lucite. The indicia is preferably engraved but may be painted, if desired. Knobs 22 are fastened to the window to facilitate the rotation thereof.

An additional feature of the present method of attack is that it permits the use of short range classification devices. Weapons such as homing torpedos are very expensive and are often wasted on false targets which long range sonar equipment alone cannot distinguish from real ones. Auxiliary devices, which detect submarines by magnetic anomalies, temperature changes or chemical variations induced in the surrounding media; have been developed. By mounting such a device, for example, a total field magnetometer, on the weapons carrier an additional target characteristic may be checked at close range between the time the posit buoy is dropped and the time the weapon is dropped. High resolution short range sonar is also suitable for this purpose. By long range a distance of many miles, eg more than 5 miles, is inferred, while short range classification means generally would be most effective under a mile from target.

If the classification device does not confirm the sonar contact, the weapon is not released. Again most of these devices have been designed to produce an electrical signal, so that they are easily incorporated in an automatic system by those skilled in the art. Performance tests have proved that such classification devices more than justify their extra expense in avoiding the waste of weapons, not to mention the possible consequences of attacking an unknown target.

While the sonar has been described as stationary or mounted on a slow moving vehicle, the method is also employed to advantage with two high speed vehicles. Both vehicles are equipped with long range sonar antisubmarine weapons and posit buoy or the like. The vehicles are employed as shown in FIGS. la through If. If an attack is not successful, the vehicles exchange their modes of operation and initiate a new attack.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim:

I. A. method of locating, classifying and possibly destroying a distant underwater object comprising, locating approximately the position of said object by means of a substantially stationary long range sonar equipment, dispatching a high speed vehicle carrying a small sonar transponder and weapon to the approximate location of said object as established by sonar, dropping said sonar transponder into the water near the position of said object, locating approximately the position of said transponder by means of said sonar equipment, transmitting the range and bearing between said object and said transponder by means of electromagnetic waves to said vehicle, whereby said vehicle may quickly and accurately be directed to deliver said weapon to said object.

2. The method according to claim 1 wherein said high speed vehicle is dispatched through the air.

3. The method according to claim 1 wherein said high speed vehicle is dispatched through the water.

4. The method according to claim 1 wherein the range and bearing between said object and said transponder is transmit ted to said vehicle over a radio link.

5. The method according to claim 1 wherein said high speed vehicle carries a close range means to classify underwater targets comprising the further steps of dispatching said high speed vehicle from the transponder to said object and classifying the target by means of said close range means. 

